There are conventional methods of heating a molding object filled into a mold that involve raising the temperature of the mold to heat the molding object, by circulating steam through a steam flow path provided in the mold or by circulating steam through a steam flow path provided in a member brought into contact with the outer surface of the mold, as shown in Patent Document 1.
Methods that involve heating the mold using induction heating have also been considered in recent years from the viewpoint of shortening the heating time, achieving CO2 reduction through using clean energy, and the like. Specifically, there are methods that involve arranging induction coils provided so as to surround the periphery of the mold, and passing magnetic flux that is produced by the induction coils into the mold so as to directly heat the mold with electrical heat (Joule heating) resulting from the induced current that is produced at this time, as shown in Patent Document 2 and Patent Document 3, for example.
However, there is a problem with methods that involve providing induction coils outside the mold and induction heating the mold directly in that it is difficult to efficiently pass magnetic flux that is produced by the coils into the mold, and magnetic flux that is produced by the induction coils leaks out without passing into the mold, preventing the mold from being adequately heated. Also, temperature unevenness tends to occur in the mold, preventing the molding item from being uniformly heated. Furthermore, the induction coils are corroded by corrosive gases that can exist outside the mold.